1. Field of the Invention
This invention relates to fatigue resistant fasteners, in general and fatigue resistant bolts in particular.
It is well known that structural members, including bolts, are more subject to structural failure when they are cyclically or dynamically stressed. This is particularly true with respect to bolts which have a high static design load or preload. When such bolts are tightened to their design preload and then subjected to a dynamic environment they may experience dynamic stresses than approach and even exceed the yield strength of the material from which the bolt is manufactured. This can, of course, result in structural failure.
One solution to this problem is to simply use a larger bolt. However, in may instances this is not practical or desirable. For example, in aircraft applications an undesirable weight penalty would be experienced.
2. Description of the Prior Art
Experience has shown that fatigue failure of such bolts usually occurs in the threads. Accordingly, efforts to produce fatigue resistant bolts have been concentrated on thread design. An example of a bolt having fatigue resistant threads is taught in U.S. Pat. No. 3,433,117 issued to Gowen, et al, on Mar. 18, 1969. In this invention the fatigue resistant properites of the bolt were obtained through certain modifications as to the form and relative arrangement of the threads.